Nitrogen trifluoride (NF.sub.3) is generally used as a dry etching gas or a reactor chamber cleaning gas in the manufacture of semiconductors. The etching of silicon with an ionized reactive gas, such as NF.sub.3, gives volatile reaction products. This is desirable because unlike earlier methods of etching in a fluorocarbon plasma, chances for fouling of wafer surfaces with reaction by-products, such as carbon and sulfur are eliminated, and accordingly the etching speed is expedited. For this reason, NF.sub.3 gas is currently used more often, but since NF.sub.3 is highly stable at ordinary temperatures, it is not decomposed in the atmosphere, and thus contributes to global warming of the environment. Moreover, although NF.sub.3 is not flammable, NF.sub.3 is toxic with a maximum allowable concentration of 10 parts per million. Therefore, disposal of waste NF.sub.3 is desirable and has represented a problem for the semiconductor and industrial gas industries.
U.S. Pat. No. 5,417,948 discloses the use of zirconium alloys to abate NF.sub.3. It lists fluidized beds as a possible means of contacting the alloys with NF.sub.3. A control example used iron wire cut into 5 to 10 mm pieces as a bed material.
Japanese Patent Publication H7-155,542 discloses the use of chromium, manganese, iron, aluminum, cobalt, nickel, copper, zinc, palladium and tin to abate NF.sub.3 at 150 to 500.degree. C. with a surface area of 1 m.sup.2 /g or greater.
U.S. Pat. No. 5,176,889 discloses the use of carbonaceous materials to convert NF.sub.3 to CF.sub.4 and nitrogen.
Japanese Patent Publication 2-30731 discloses the abatement of NF.sub.3 using activated carbon and charcoal of 4 to 8 mesh (4.7 to 2.4 mm).
Japanese Patent Publication 07155,540 discloses the use of mixtures of metal fluorides and reduced metals including iron, aluminum, manganese and palladium, and fluorides of zirconium, sodium, zinc, aluminum and calcium to abate NF.sub.3.
Japanese Patent Publication 07155,541 discloses the use of metal hydroxides and oxides to abate NF.sub.3. Chromium, iron, zirconium, and manganese oxide and iron hydroxide are mentioned.
Shen, et. al., Nanosize Silicon Whiskers Produced by Chemical Vapor Deposition: Active Getter for NF.sub.3, Chemistry of Materials, (1995), Vol. 7, pp. 961-968 describes the use of silicon whiskers of 120-300 .ANG. (0.012 to 0.030 microns) to abate NF.sub.3. The smaller diameter silicon whiskers were determined to be the most active NF.sub.3 getters.
Vileno, et.al., Thermal Decomposition of NF.sub.3 with Various Oxides, Chemistry of Materials, (1996) Vol. 8, pp. 1217-1221, describes the use of various oxides to abate NF.sub.3. The oxides included aluminas, calcium oxides and zeolites.
Vileno, et.al., Thermal Decomposition of NF.sub.3 by Ti, Si, and Sn Powders, Chemistry of Materials, (1995) Vol. 7, pp. 683-687, describes the use of various powders to abate NF.sub.3. The powders included titanium, silicon and tin of 45 microns.
The prior art has attempted to provide various methods and means of abating NF.sub.3. However, the prior art has not achieved a commercially viable process for NF.sub.3 abatement which generates no pollutants, allows for high throughput, avoidance of clogging, efficient destruction of NF.sub.3 and a method for recharging of the abatement system for continuous processing. These advantages are achieved by the present invention, as will be set forth in greater detail below.